Microenvironments play a role in modulating cell growth, differentiation and activity. However, current in vitro environments used to culture cells fail to provide optimal microenvironments to simulate in vivo cell/tissue growth and differentiation. Cell culture techniques and the understanding of the complex interactions cells have with one another and the surrounding environment have improved in the past decade. There is now a better understanding of the role extracellular matrix materials play in the proliferation and development of artificial tissues in vitro. Historically cell culture techniques and tissue development fail to take into account the necessary microenvironment for cell-cell and cell-matrix communication as well as an adequate diffusional environment for delivery of nutrients and removal of waste products.
While many methods and bioreactors have been developed to grow tissue masses for the purposes of generating artificial tissues for transplantation or for toxicology studies, these bioreactors do not adequately simulate in vitro the mechanisms by which nutrients and gases are delivered to tissue cells in vivo.